Two of California's largest utilities are now getting 20% of their energy from renewables as required by the state's Renewable Portfolio Standard (RPS) - 20% by 2010.

Ok, they're a year late, but Southern California Edison and San Diego Gas & Electric Co. hit the target in 2011. Pacific Gas and Electric (PG&E) will get there in 2012.

That's pretty impressive considering the law was passed five years ago (in 2006) and 10 years ago, San Diego Gas & Electric sourced just 1% from renewables. Now, it's 1.4 million customers get 20% of their electricity from renewables.

Although 29 states and Washington DC have an RPS, most are in the low, single digits. Still, most states are on track to meet those mimimal standards, which together would result in 115 gigawatts of renewable energy by 2025 - representing billions in investments and clean energy jobs.

But California is one of the few states to raise the bar as the target gets close to being met - here's why that's important.

Once utilities get close to the mandated target they tend to pull back on further investments and even reduce incentives for homeowners and businesses to install clean energy.

Take Colorado, where some utilities are close to achieving its RPS of 30% by 2020. That achievement represents $1 billion in investment, but few see utilities continuing to spend that once the goal has been met. Instead, renewable energy tends to plateau instead of continuing to rise.